<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      let x = 1;
      function func() {
        var x; // undefined
        console.log(x); // undefined
        // let x = 2;//不会变量提升
        // var x = 2; //会变量提升
        x = 2;
        console.log(x); //2
      }
      func(); //1
    </script>
  </body>
</html>
